A thermosiphon reboiler can be used in certain instances to save pumping costs in a fractionation column. The reboiler forms one hydraulic leg and the column another in a U-shaped "siphon" network. As vapor return lowers the hydraulic head of the reboiler leg, additional liquid feeds hydraulically from the fractionator to maintain a head equilibrium between the legs. Such thermosiphon reboilers are well known in the art.
Thermosiphon reboilers are commonly used on a variety of distillation towers in manufacturing processes. Increased efforts to improve energy efficiency in the processes have resulted, in some instances, in an addition of multiple separate reboilers piped in parallel with a common feed line so that several different hot process and/or utility streams can be used as heating fluids by supplying each of the hot streams to a separate reboiler. Therefore, reboil flowrate through each of the individual reboilers depends on a complicated resolution of the head differentials in each parallel leg. It can be seen that carefully balanced piping schemes and complex flow controls must be used to maintain adequate flow through each reboiler as process conditions change. Even so, flow upset and startup difficulties can still frequently occur. It is therefore desirable to reduce piping and control complexities as well as opportunity for process upset due to flow imbalances by integrating separate heat exchangers into a single unit.
U.S. Pat. No. 5,048,601 to Yamaguchi et al. describes a shell-and-tube reactor including a vessel having at least one intermediate tube plate sectioning the interior of the vessel into at least two compartments having different temperatures.
U.S. Pat. No. 5,037,955 to Dighton et al. describes a single pass, horizontal shell and tube heat exchanger made in three sections which can be independently heated.
U.S. Pat. No. 3,832,289 to Kays et al. describes preheater for use in a multieffect distillation system comprising a housing having a plurality of chambers with a conduit means extending axially through each of the chambers
U.S. Pat. No. 2,204,447 to Samans describes a compact catalytic reactor apparatus for securing uniform heat exchange throughout the body of the catalyst. The apparatus has a shell divided into a plurality of cylindrical sections surrounding a tube bundle with catalyst in the spaces between the tubes.
U.S. Pat. No. 2,132,150 describes a method and apparatus for contacting liquid phases wherein the contact zone comprises packing members which may be segregated from each other in separate casings.